Chemistry Paper 2 Consolidation

Question 1

The amount of water vapour in today’s atmosphere is much less than the amount in the Earth’s early atmosphere.

Explain why the amount of water vapour in the atmosphere has decreased.

Answer 1

• Earth cooled / temperature decreased
• Water vapour condensed / oceans formed

Question 2

Describe what you would see if damp, blue litmus paper is placed into chlorine gas.

Answer 2

Litmus paper turns from blue to red first, then from red to white

Question 3

Describe what is meant by a covalent bond.

Answer 3

• Shared electrons
• A pair of / two electrons

Question 4

Explain why chlorine is a gas, rather than a liquid, at room temperature.

Answer 4

• Intermolecular forces / forces between molecules
• Intermolecular forces are weak and take little energy to break
• Chlorine has a boiling point below room temperature

Question 5

When the gas hydrogen chloride, HCl, is dissolved in water, a solution forms. Blue litmus paper dipped in this solution turns red.

State why the litmus paper turns red.

Answer 5

Solution is acidic and contains H+ ions

Question 6

Explain the trend between the alkanes’ boiling points and the no. of carbon atoms in one molecule of each alkane.

Answer 6

• Boiling points increase as the number of carbon atoms (per molecule) increases
• Because stronger forces between molecules / increased intermolecular forces

Question 7

Describe what is seen when chlorine water is added to potassium bromide solution and the mixture shaken.

Answer 7

• Potassium bromide solution is colourless
• Mixture turns yellow/ orange

Question 8

A solid ionic compound is dissolved in water to form a solution.
Describe a simple experiment to show that charged particles are present in this solution.

Answer 8

• Insert electrodes into aqueous solution
• Connect to electrical supply
• Bulb lights

Question 9

Explain why the mass of products might be greater than the mass of reactants in an experiment.

Answer 9

Other gases could have also reacted

Question 10

Explain how carbon dioxide is released into the atmosphere

Answer 10

Complete combustion of fuels/wood/rubbish/plastic

Question 11

Iron reacts with oxygen to form iron oxide, iron wool was placed in the bottom of a wet test tube. The test tube was then put in a beaker of water. After some time the water level in the test tube rose and some of the iron wool had formed an iron oxide.

Explain why the water level in the test tube rose during the experiment.

Answer 11

• Oxygen is removed from air to oxidise iron
• Water rises to fill space

Question 12

Iron reacts with oxygen to form iron oxide, iron wool was placed in the bottom of a wet test tube. The test tube was then put in a beaker of water. After some time the water level in the test tube rose and some of the iron wool had formed an iron oxide.

What gas would mostly remain in the test tube at the end of the experiment?

Answer 12

Nitrogen

Question 13

Lithium, potassium and rubidium are alkali metals.

Describe what you would see when a small piece of rubidium is dropped onto water.

Answer 13

• Effervescence
• A flame is ignited

Question 14

Explain, in terms of bond breaking and bond making, why some reactions are exothermic.

Answer 14

• Breaking bonds needs energy, which is provided from endothermic reactions
• Making bonds releases energy, which is done in exothermic reactions
• More energy is released than absorbed in an exothermic reaction

Question 15

Bromine reacts with hydrogen to form hydrogen bromide. Hydrogen bromide dissolves in water to form a solution.

State the name of the solution formed.

Answer 15

Hydrobromic acid

Question 16

Elements in group 3 of the periodic table are boron, aluminium, pallia, indium and thallium. Elements can declassified as metals or non metals.

Explain, using its position in the periodic table, whether indium is a metal or a non-metal

Answer 16

• Metal
• Indium is on the left/ below the line dividing metals and non-metals

Question 17

Describe what would be seen when a piece of calcium is dropped into a container of water.

Answer 17

• Effervescence as hydrogen is produced
• A white precipitate is formed as calcium hydroxide appears

Question 18

Magnesium oxide has a melting point of 2852 degrees Celsius.

Explain why magnesium oxide has such a high melting point.

Answer 18

A large amount of energy is required to overcome the strong electrostatic forces between 2+ cations and 2- anions

Question 19

Describe the properties of an alkane and an alkene.

Answer 19

• Alkane is a saturated molecule that contains a single covalent bond between two carbon atoms
• Alkene is an unsaturated molecule that contains a double covalent bond between two carbon atoms

Question 20

Sodium thiosulfate solution, Na2S2O3, reacts with dilute hydrochloric acid. Na2S2O3 (aq) + 2HCl (aq) → 2NaCl (aq) + H2O (l) + SO2 (g) + S (s). When dilute hydrochloric acid is mixed with sodium thiosulfate solution, the mixture turns cloudy.

Explain why the mixture turns cloudy.

Answer 20

A solid sulphuric precipitate is formed

Question 21

In an investigation, different concentrations of hydrochloric acid are reacted with sodium thiosulfate solution. The mixture goes cloudy at different rates.

Describe how the rate at which the mixture goes cloudy can be measured.

Answer 21

• Flask placed over/ in front of cross
• Measure time when cross is obscured

Question 22

What are the three most common gaseous elements in air?

Answer 22

• Nitrogen
• Oxygen
• Argon

Question 23

The flask is used for an experiment to find the density of argon. The flask holds 250.0 cm^13 when filled up to the line. There is an error in the volume the student has used in the calculation. This would give an incorrect value for the density of argon.

Identify this error and state what should be done to correct it.

Answer 23

• Volume of flask is more than 250 cm^3
• Measure the whole volume of the flask